The present invention relates generally to a spool valve arrangement and, more particularly, to a construction in which the switching operation of such a valve is accomplished smoothly and quietly.
It is known in the prior art to smooth the operation of a valve in a fluid system by damping the movement of the spool slide so as to prevent shockwaves from disturbing the effective running of the fluid system. A spring-loaded piston is slidingly received in a flowrestrictor sleeve mounted on the valve. As the piston moves in the sleeve, a different flow-through crosssection is presented to the fluid.
This prior-art arrangement is not only quite expensive, but has the added disadvantage that it is quite jerky and noisy in operation. As pressurized fluid escapes from an outlet towards its respectively associated return-flow or pressure-relief chamber, the pressurized fluid immediately acts upon an adjacent end of the spool slide and tends to accelerate the movement of the slide. Thus, the slide is very rapidly moved towards one of its operative positions, thereby causing undesirable impulses and shockwaves in the fluid system.